Textured yarn and process for its manufacture

ABSTRACT

The invention comprises textured continuous filament yarns of a synthetic thermoplastic material, especially a polyester such as polyethylene terephthalate in which each filament comprises, on the microscopic scale, alternating zones whose diameter increases and decreases progressively between at least two different mean values, the zones of smaller diameter corresponding to zones of higher crystallinity index and higher molecular orientation and vice versa, each filament having a large apparent bulk, and the yarn as a whole having tridimensional crimp. Preferably the filaments have similar, though somewhat attenuated, differences along their length on a macroscopic scale, giving them a knop appearance. The yarns are made by partially stretching a multifilament yarn in the presence of a crack-producing agent, such as an aqueous lower alkanol at ambient temperature, giving the partially stretched yarns a thermal treatment in a relaxed condition, and subjecting them to a twist-set-untwist treatment, in which the heat setting step may also provide part of or the whole of the said thermal treatment.

United States Patent [72] lnventor Michel Buzano Villeurbanne, France [2]] Appl. No. 829,752 [22] Filed June 2, 1969 [45] Patented Dec. 28', 1971 [73] Assignee Societe Rhodiaceta Paris, France [32] Priority June 6, 1968 [33] France [31] 50070 [54] TEXTURED YARN AND PROCESS FOR ITS MANUFACTURE 18 Claims, No Drawings [52] US. Cl 57/140 R, 57/ l 57 T5 [51 1 lnt. Cl D02g 3/34, 002g 1/02, D02j 1/06 [50] Field of Search 57/140, 140 T, 140 .l, 157, 35, 36, 39, 51

[56] References Cited UNITED STATES PATENTS 7 2,296,394 9/1942 Meloon 57/140 UX 2,917,779 12/1959 Kurzke et al... 57/140 UX 3,241,305 3/1966 lrwin et al. 57/140 3,263,298 8/1966 Holton 57/140 X 3,439,489 4/1969 Holton et a1. 57/140 FOREIGN PATENTS 682,717 3/1964 Canada 57/140 Primary Examiner-Donald E. Watkins At/orney-Cushman, Darby & Cushman ABSTRACT: The invention comprises textured continuous filament yarns of a synthetic thermoplastic material, especially a polyester such as polyethylene terephthalate in which each filament comprises, on the microscopic scale, alternating zones whose diameter increases and decreases progressively between at least two different mean values, the zones of smaller diameter corresponding to zones of higher crystallinity index and higher molecular orientation and vice versa, each filament having a large apparent bulk, and the yarn as a whole having tridimensional crimp. Preferably the filaments have similar, though somewhat attenuated, differences along their length on a macroscopic scale, giving them a knop appearance. The yarns are made by partially stretching a multifilament yarn in the presence of a crack-producing agent, such as an aqueous lower alkanol at ambient temperature, giving the partially stretched yarns a thermal treatment in a relaxed condition, and subjecting them to a twist-set-untwist treatment, in which the heat setting step may also provide part of or the whole of the said thermal treatment.

TEXTURED YARN AND PROCESS FOR ITS MANUFACTURE This invention relates to novel resilient or elastic textured yarns having a large apparent bulk and helical, tridimensional crimp, to woven and knitted articles comprising them, and to their manufacture.

Hitherto, resilient, helically crimped, textured yarns have been produced by twisting, setting and untwisting yarns consisting of continuous filaments made from a synthetic thermoplastic material. A technique of this kind can be performed either continuously or discontinuously, depending on the effects which are desired, and gives good results so that it forms current industrial practice.

Unfortunately, in particular when texturing by the false twist technique (which is effected continuously), the setting or fixing temperatures are generally high, being near the fusion temperature of the material employed. For example, in the case of polyethylene terephthalate and nylon-6,6 the yarns are conveyed through ovens at a temperature of above 200200 C. Even more disadvantageous is the fact that, especially in treating polyethylene terephthalate yarns, an extremely precise adjustment of the setting temperature, to within about 1, is required if the yarn obtained is to have uniform properties, in particular dyeing affinity. Such precise adjustment is made more difficult by the fact that present day production speeds for textured yarns are above 100 m./min., and the heat losses due to the travelling yarn are considerable.

In one aspect the present invention consists in a yarn comprising continuous synthetic thermoplastic filaments, each of which comprises, on a microscopic scale, alternating zones whose diameter increases and decreases progressively between at least two different mean values, the zones of smaller diameter corresponding to zones of higher crystallinity index and degree of molecular orientation and vice versa, each filament having a large apparent bulk, and the yarn as a whole having a three-dimensional crimp.

The yarn may be a knop yarn, and exhibit, on a macroscopic scale, an alternation of thin and thick portions, the said thin and thick portions having, microscopically, the same kind of structural differences as defined above for the microscopic alternating zones, though these differences are less pronounced in the thin portions and may even be absent, these portions then being completely drawn or stretched.

The yarns may be made of any synthetic, thermoplastic material, such as a polyester or polyamide, especially polyethylene terephthalate.

The invention consists also in a process for the preparation of these yarns, which comprises partially stretching a multifilament synthetic thermoplastic yarn in contact with a crackpromoting agent, thermally treating the yarn in a relaxed state, and subjecting it to a treatment involving successively twisting, setting and untwisting. The twisting, setting and untwisting treatment may be effected discontinuously or continuously, notably by a false twist technique. The order in which the various treatments are performed can be varied, so long as the thermal treatment or treatments and the twist-set-untwist treatment follow the initial partial stretching.

The thermal treating in the relaxed condition may be combined with the twist fixing or setting treatment. It may be effected in one or more stages. In the latter case, one stage at least may be effected before the twisting, setting and untwisting treatment, the further stage or stages being effected as the setting step of even after the untwisting step. It may be combined with any other treatment, such as dyeing, etc. Furthermore, the yarn obtained may be subjected to subsequent thermal treatment in the tensioned state, if it is desired to diminish its elasticity.

The crack-producing agent may be of any known type, such as is described in the literature, but is preferably of a type readily manipulated and inexpensive, such as a lower alcohol in aqueous solution.

The optimum degree of stretch in the initial partial stretch will depend on the nature and count of the yarn. With a polyethylene terephthalate yarn of normal count, Le, a count per filament lower than 15 dtex, the degree of stretch is advantageously between 2 and 3.5. This initial stretch may be effected in one or a number of stages.

If the degree of stretch is varied, and/or if the yarn is thermally treated with a varying degree of relaxation or with alternate stretching and relaxation before the twisting, setting and untwisting treatment, there is obtained a textured, highbulk, false twist, knop yarn that is particularly advantageous for numerous applications.

It is a surprising advantage of the process that it permits the manufacture of a textured, elastic, helically crimped yarn using a twist-setting temperature which is substantially lower than the conventionally employed. In particular it can be much lower than the fusion temperature of the yarn.

The setting temperature required depends to some extent on the treatment conditions such as the degree of stretch. For a polyethylene terephthalate yarn of normal count, and a degree of stretch as indicated above, it can advantageously be lower than 150 C. and is preferably between and C.

If so low a setting temperature were used in the conventional false twist process, the manufacture of elastic textured yarn would be impossible, whereas if the process of the invention is used, a yarn can be obtained whose properties are perfectly acceptable for its subsequent use for textile purposes.

The invention is illustrated in the following examples.

EXAMPLE 1 A 44 filament polyethylene terephthalate yarn of filament count 7.8 dtex *(7 denier) is stretched in an aqueous bath containing 25 percent of ethanol at ambient temperature, in one run to a degree of 2.8 and in a second to a degree of2.9.

The yarn is then passed through a conventional false twist device comprising a spindle having crossed bars and rotating at 70,000 r.p.m.

The twist imparted to the yarn is of the order of 2,290 turns per meter Z-twist. The overfeed in the setting oven is 2 percent and the oven temperature is 110 C. The winding up overfeed of the yarn is 14 percent.

For comparison, a standard 144 dtex denier)/44 filament yarn is given the same false twist treatment. The results are shown in the following table:

Reference Yarn according to the yarn invention Degree of Degree 01 stretch stretch Exact count (denier) I3} 133 I37 High-bulk effect, 9,57 36% 28% Simple bulk cmlg. 2 9 3.1 2.8

EXAMPLE 2 A 22 filament polyethylene terephthalate yarn of filament count 7.8 dtex (7 denier) is stretched to a degree of 3 in an aqueous solution comprising 25 percent of ethanol at ambient temperature and is then passed through a false twist device and set.

Two yarns l and 2 were obtained in this way, and two reference yarns l and 2 were obtained by giving a dtex (45 denier) 22 filament polyethylene terephthalate yarn substantially the same false twist treatment, apart from the degree of twist. The conditions of the treatment are shown in the following table:

It will be seen that the yarns 1 and 2 of the invention have a much better high-bulk effect than the reference yarns. They are very suitable for use for textile purposes, which the reference yarns are not.

Furthermore, since the setting temperature is relatively low, it is possible to dye the yarns subsequently at a temperature higher than the setting temperature; this has the considerable advantage of eliminating irregularities in dyeing affinity.

Iclaim:

1. Continuous filament textile yarns of polyester in which each filament comprises, on the microscopic scale, alternating zones whose diameter increases and decreases progressively between at least two different mean values, the zones of smaller diameter corresponding to zones of higher crystallinity index and higher molecular orientation and vice versa, each filament having throughout its length a large apparent bulk, and the yarn as a whole having a continuous tridimensional crimp.

2. Yarns according to claim I, in which the filaments have, on a microscopic scale, alternations of thin and thick portions having the same structural differences as defined in claim 1 for the microscopic scale except that the structural differences are attenuated in the thin portions, the said yarns having a knop appearance.

3. Yarns according to claim 2, in which the said structural differences in the thin portions are attenuated substantially to zero.

4. Yarns according to claim 1, in which the filaments are of polyethylene terephthalate.

5. Yarns according to claim 2, in which the filaments are of polyethylene terephthalate.

6. Process for the production of textured continuous filament polyester yarns, which comprises, as the sole stretching operation, partially stretching in at least one stage a continuous filament polyester yarn of filament count below 15 dtex by a factor of 23.5x and in contact with a crack-producing agent, thermally treating the yarn in a relaxed condition, and subjecting the yarn to a treatment comprising twisting, setting and untwisting.

7. Process according to claim 6, in which the thermal treatment is effected on the running yarn.

8. Process according to claim 6, in which the thermal treatment is, at least in part, combined with the setting step of the twisting, setting nd untwisting treatment.

9. Process according to claim 6, in which a polyethylene terephthalate yarn is treated.

10. Process according to claim 9, in which the degree of stretch in the initial partial stretching step is between 2 and 3.5, and the setting temperature used in the twist-set-untwist treatment is l 50 C.

11. Process according to claim 10, in which the setting temperature is 90-l 25 C.

12. Process according to claim 6, in which the yarn is stretched to a varying degree in contact with the crackproducing agent.

13. Process according to claim 6, in which the yarn is given a thermal treatment under conditions such that the alternation in its length during the operation varies with time.

14. Process according to claim 13, in which during the said thermal treatment the yarn is alternately relaxed and stretched to a varying degree.

15. Process according to claim 6, in which the crackproducing agent is an aqueous lower aliphatic alcohol, and the initial partial stretch is effected at ambient temperature.

16. Process according to claim 11, in which the yarn is stretched to a varying degree in contact with the crackproducing agent.

17. Process according to claim 11, in which during the said thermal treatment the yarn is alternately relaxed and stretched to a varying degree.

18. Process according to claim 11, in which the crackproducing agent is an aqueous lower aliphatic alcohol, and the initial partial stretch is effected at ambient temperature. 

2. Yarns according to claim 1, in which the filaments have, on a microscopic scale, alternations of thin and thick portions having the same structural differences as defined in claim 1 for the microscopic scale except that the structural differences are attenuated in the thin portions, the said yarns having a knop appearance.
 3. Yarns according to claim 2, in which the said structural differences in the thin portions are attenuated substantially to zero.
 4. Yarns according to claim 1, in which the filaments are of polyethylene terephthalate.
 5. Yarns according to claim 2, in which the filaments are of polyethylene terephthalate.
 6. Process for the production of textured continuous filament polyester yarns, which comprises, as the sole stretching operation, partially stretching in at least one stage a continuous filament polyester yarn of filament count below 15 dtex by a factor of 2-3.5x and in contact with a crack-producing agent, thermally treating the yarn in a relaxed condition, and subjecting the yarn to a treatment comprising twisting, setting and untwisting.
 7. Process according to claim 6, in which the thermal treatment is effected on the running yarn.
 8. Process according to claim 6, in which the thermal treatment is, at least in part, combined with the setting step of the twisting, setting nd untwisting treatment.
 9. Process according to claim 6, in which a polyethylene terephthalate yarn is treated.
 10. Process according to claim 9, in which the degree of stretch in the initial partial stretching step is between 2 and 3.5, and the setting temperature used in the twist-set-untwist treatment is 90*-150* C.
 11. Process according to claim 10, in which the setting temperature is 90*-125* C.
 12. Process according to claim 6, in which the yarn is stretched to a varying degree in contact with the crack-producing agent.
 13. Process according to claim 6, in which the yarn is given a thermal treatment under conditions such that the alternation in its length during the operation varies with time.
 14. Process according to claim 13, in which during the said thermal treatment the yarn is alternately relaxed and stretched to a varying degree.
 15. Process according to claim 6, in which the crack-producing agent is an aqueous lower aliphatic alcohol, and the initial partial stretch is effected at ambient temperature.
 16. Process according to claim 11, in which the yarn is stretched to a varying degree in contact with the crack-producing agent.
 17. Process according to claim 11, in which during the said thermal treatment the yarn is alternately relaxed and stretched to a varying degree.
 18. Process according to claim 11, in which the crack-producing agent is an aqueous lower aliphatic alcohol, and the initial partial stretch is effected at ambient temperature. 